Which speaker should be on top?

I think there may be a PARC in your future. With that much bass energy you will certainly be exciting the room modes.

You're right about taking the false corner to the ceiling. In this way both the K-horn and the TacT sub will have three reflective sides. The K-horn will have the two false walls and the floor, while the sub will have the two false walls and the ceiling. The false walls will be made of two layers of 3/4 inch high density melomine particle board glued together to eliminate any resonance. Each side of the false walls will be 3 and a half feet long. With this arrangement I'll be feeling organ music, not hearing it. Thank goodness for the Isowall treatment. Rives, I guess I'll need your bass correction devise to make sure the bass remains flat.

The area of greatest concern is the false corners, what is behind them and it sounds like there is a foot between them and the ceiling. Why not take them up to the ceiling (seven foot false corners) I'm assuming that's height--but that's the area I'm not sure I understand completely. I can certainly understand the use of the ISO wall, but have you considered other sources of sound leakage? It's really hard for me to comment without knowing just about everything about the room--it all works together and sometimes one thing that might seem insignificant can through the whole thing off--that's why I'm cautious about commenting when I don't have all the facts.

Thanks Rives. What else do you need to know about the room?
In general the room dimension is 8/13/17 feet. The room has the ASC isowall acoustic system.

The dominant not submissive the speaker.

Subs on top. The K-horn tweeter and midrange does not have a wide vertical dispersion, raising the height signficantly will create significant sound degredation. In addition to this the K-horn needs 3 reflective (bass supportive) walls, thus needs to be on the floor. The tact sub is less critical and actually may benefit from being higher, though without knowing everything else about the room I can't be sure that is true.